This invention relates to the preparation of impregnated, substantially spherical alumina-containing particles having improved crush strength retention. In another aspect, this invention relates to a process for hydrotreating hydrocarbon-containing oils, which also contain sulfur and metal impurities, in the presence of a fixed bed comprising at least one layer of impregnated, substantially spherical alumina-containing particles. In still another aspect, this invention relates to the use of said at least one layer of impregnated, substantially spherical alumina-containing particles as support layer in a fixed catalyst bed. In a further aspect, this invention relates to a process for catalytically hydrotreating hydrocarbon-containing oils in the presence of water. In still another aspect, this invention relates to a fixed multi-layer hydrotreating catalyst bed system comprising at least one layer of substantially spherical alumina-containing particles.
Fixed beds of hydrotreating catalysts are used in many oil refineries. Examples of processes in which fixed hydrotreating (hydrofining) catalyst beds are used include hydrodenitrogenation, hydrodesulfurization and hydrodemetallization of heavy oils. Generally, a layer of shaped, substantially inert ceramic particles at the bottom of the fixed bed reactor is used to support a column of one or more layers of hydrotreating catalyst. The same shaped, substantially inert material can also be employed as the top layer (i.e., above one or more layers of hydrotreating catalyst) or between layers of hydrotreating catalyst, so as to provide improved flow dispersion of feed oil passing downwardly through the fixed catalyst bed. More recently, promoted alumina spheres, which offer some catalytic activity, have been suggested as replacement for these substantially inert ceramic support particles which generally have little or no catalytic activity for hydrodesulfurization and -demetallization. However, there is an ever present need to develop improved substantially spherical alumina-containing support particles having higher crush strength and higher resistance to specific feed components, such as water, than those presently known, so as to employ these improved alumina-containing support particles under very severe hydrotreating conditions.